@article{DAN_1981_257_2_a4,
     author = {P. I. Lizorkin and S. M. Nikol'skii},
     title = {Elliptic equations with degeneracy. {Differential} properties of solutions},
     journal = {Doklady Akademii Nauk},
     pages = {278--282},
     publisher = {mathdoc},
     volume = {257},
     number = {2},
     year = {1981},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1981_257_2_a4/}
}